This invention is generally directed to single component toner compositions, and more specifically conductive single component magnetic toner compositions wherein release fluids such as silicone oils are adsorbed on conductive pigment particles selected for the compositions. Accordingly, in one embodiment the present invention is directed to a toner composition comprised of a blend of resin particles; magnetite particles, optional external additive particles such as colloidal silicas, metal salts of fatty acids or metal salts; and present on the surface of the toner pigment particles having absorbed thereon release fluids, inclusive of silicone oils. One important magnetic toner composition of the present invention contains therein a mixture of resin particles; magnetite particles; and present on the surface thereof pigment particles which have absorbed thereon release fluids, including those fluids selected as fuser oils for an electrophotographic imaging apparatus, such as those available from Xerox Corporation as the 9200.RTM.. The aforementioned toner compositions of the present invention are particularly useful for affecting the development of images in imaging processes wherein fixing is affected by cold pressure methods, and with substantially no heat being utilized.
Numerous toner and developer compositions are known inclusive of those with waxes therein, reference for example British Patent No. 1,442,835. The aforementioned patent illustrates toner compositions comprised of a styrene homopolymer or copolymer resin and at least one polyalkylene compound. According to the disclosure of this patent, reference page 2, beginning at line 90, the starting polymer resin may be either a homopolymer of styrene, or a copolymer of styrene with other unsaturated monomers, specific examples of which are disclosed on page 3, beginning at line 1. Polyalkylene compounds selected for incorporation into the toner compositions disclosed in this patent include those of a low molecular weight, such as polyethylene, and polypropylenes of an average molecular weight of from about 2,000 to about 6,000.
Additionally, there is disclosed in U.S. Pat. No. 4,460,672, entitled "Positively Charged Toner Compositions", a developer composition mixture comprised of electrostatic toner particles consisting of resin particles, pigments particles, low molecular weight waxy materials with a molecular weight of from about 500 to about 20,000, and further included in the composition from about 0.5 percent by weight to about 10 percent by weight of a charge enhancing additive selected from, for example, alkyl pyridinium halides, organic sulfonate compositions, and organic sulfate compositions. The disclosure of this patent is totally incorporated herein by reference.
Magnetic single component toner compositions are also known, which compositions are generally comprised of resin particles, pigment particles, and magnetite. Thus, for example, there is disclosed in U.S. Pat. No. 3,639,245 a dry developer with a specific conductivity, and containing magnetic particles which are blended with a toner resin. Thereafter, and following pulverization the particles resulting are mixed with carbon black and small particle silicone dioxide particles for the purpose of improving flowability. Furthermore, there are disclosed in many patents similar magnetic toner compositions including those comprised of first and second resin particles, pigment particles, magnetites, and low molecular weight waxes such as polyethylenes. Also, single component developer compositions with first and second resin particles, magnetites, and islands or patches of carbon black are described in U.S. Pat. No. 4,569,896. Of interest with respect to the '896 patent is the prior art illustrated in, for example, columns 1 and 2, and the prior art listed on the first page of this patent.
Pressure fixable single component toners with polyamide resins are illustrated in U.S. Pat. No. 4,612,272. More specifically, there is disclosed in this patent a single component developer composition containing at least 50 percent of magnetic oxide, reference column 4, line 28, and a polyamide resin, see for example column 3, beginning at line 53. It is indicated in column 4 of this patent that a highly conductive carbon black pigment is added to the developer for the purpose of providing particles with a surface coating which will render them somewhat conductive. Toners containing the aforementioned polyamides are, however, pressure fixable onto coated paper, reference the working Examples thereof. In contrast, for example, toner compositions of the present invention are pressure fixable onto plain paper. Flowable pressure fixable magnetic toners are also illustrated in U.S. Pat. No. 4,262,077 containing conductive carbon black, reference the Abstract of the Disclosure. Pressure fixable toners for electrostatic development are illustrated in U.S. Pat. No. 3,775,326; and these toners may include optional additives such as metal soap, or a polyhydric alcohol, reference for example the Abstract of the Disclosure. A similar teaching is presented in U.S. Pat. No. 3,873,325. Also, in U.S. Pat. No. 4,108,653 there are described highly conductive, see column 3, beginning at line 11, pressure fixable toner compositions with polyethylene of a weight average of at least 1,500, colorants, and optional additives. In column 2, beginning at line 21, it is indicated that the toners of this patent may contain other resin binders. A similar teaching is present in U.S. Pat. No. 4,355,088. Other patents of interest include U.S. Pat. No. 3,925,219 wherein there is described a toner with a low molecular weight polyethylene, Elvax, and magnetite, reference working Example V; U.S. Pat. Nos. 3,829,314; 3,854,975; 3,873,325; 4,022,738; 4,100,08; 4,206,247; 4,262,077; 4,385,107; 4,397,941; Japanese Abstracts 56-165152, 54-48245, and 56-55954; and 4,529,680.
Of particular interest with respect to the toner compositions of the present invention is U.S. Pat. No. 4,517,272, which illustrates toner compositions with a binder polymer and a low surface energy liquid, such as a silicone oil. According to the teachings of this patent, reference column 1, line 61, the invention provides a novel developer with a toner containing a low surface energy liquid in contact with the polymer resin selected for the toner, some of which is on the surface, and some of which is occulated within the polymer particles. Since the toner compositions of this patent is believed to be insulating, that is such a composition has a resistivity of from 10.sup.12 to about 10.sup.14 ohm-cm, it is not useful as a cold pressure fixable toner for permitting the development of images in ionographic systems, such as those utilized in commercially available Delphax printers. In contrast, the toner compositions of the present invention are conductive, that is they possess a resistivity of from 10.sup.4 to 10.sup.7 ohm-cm, thus enabling development of latent images with no background deposits. With further reference to U.S. Pat. No. 4,517,272, there is described therein electrostatic dry toner compositions comprising finely divided polymeric particles admixed with a silicone oil, reference for example column 1, beginning at line 65, and continuing on to column 2, line 41. The inclusion of silicone oils into toners is also described in U.S. Pat. No. 4,568,625, and the corresponding Japanese priority document 59/200, 251-A.
Also, it is known that developer compositions can be selected for rendering visible electrostatic images on a dielectric drum, reference U.S. Pat. No. 4,496,236, the disclosure of which is totally incorporated herein by reference, and wherein there is selected a developer housing such as that described in U.S. Pat. No. 4,692,017, the disclosure of which is totally incorporated herein by reference. Thereafter, the resulting developed latent image can then be transferred directly to a permanent substrate such as paper by contact with the dielectric drum while applying pressure through, for example, a backup roll. This type of development is commonly referred to as transfix. Additionally, in situations where all of the toner is not removed to the paper, that is there remains some toner on the dielectric drum, this has been referred to in the art as offsetting, which is undesirable.
During hot roll fusing, offsetting can be avoided by selecting certain types of fuser rolls the surfaces of which can be covered with a thin film of an offset preventing liquid such as a silicone oil. This approach has been found to be highly effective, however, a comparable process is not usually selected when dielectric drums are utilized since, for example, the oil film will radically alter the characteristics of the dielectric surface and render it unsuitable for a sustained ionographic imaging. Furthermore, the use of silicone oils requires additional components to dispense and meter the oil. It is also known that additives such as metal soaps can be added to the surfaces of toner compositions, which soaps function as a release agent during transfix, reference U.S. Pat. No. 4,355,088; however, although offsetting is prevented using such soaps, dirt is generated which can contaminate and shorten the useful life of other subsystems in the imaging apparatus.
Accordingly, there is a need for improved single component pressure fixable toner compositions that can be selected for ionographic apparatuses, wherein the toner is transferred directly from the dielectric surface to the paper, and permanently affixed to the paper; and wherein silicone oil release devices are avoided. Additionally, there is a need for improved toner compositions with stable triboelectric charging characteristics, wherein surface additives are not a source of machine dirt, and wherein offsetting is substantially avoided. There also is a need for improved toner compositions which can be selected for the development and fixing in ionographic imaging processes wherein the toner particles utilized are substantially free of agglomeration. Furthermore, there is a need for toner compositions comprised of resin particles, which have incorporated thereon a release agent thereby preventing the release oil from migrating within the machine environment. There also remains a need for toner compositions which will not agglomerate or stick together when a release agent such as a mineral oil or silicone oil is selected. Furthermore, there is a need for toner compositions with specific conductivities, and wherein images of excellent resolution with substantially no background deposits are obtained. There is also a need for cold pressure fixable toner compositions with a magnetic component therein, which compositions are substantially completely transferred to a suitable substrate subsequent to development. Additionally, there is a need for single component toner compositions wherein toner offsetting problems are substantially eliminated. In addition, there is a need for toner compositions wherein small amounts of oils can be selected while simultaneously providing sufficient release characteristics for the compositions without adversely effecting pressure fixability, and eliminating undesirable offsetting problems. Furthermore, there is a need for single component cold pressure fixable toner compositions with a resistivity of from 10.sup.4 to 10.sup.7 ohm-cm, which enables excellent development, and wherein undesirable background deposits are eliminated. There is also a need for toner compositions with binder resins which can be micronized by, for example, air attrition to about 10 to 30 microns average diameter. Additionally, there is a need for pressure fixable toner compositions wherein the toner particles do not agglomerate upon storage at elevated temperatures.